JPH04282206A - Changing-over extruding method for parison - Google Patents

Abstract

PURPOSE:To perform the changing-over between multilayer parison and single- layer parison in a short period of time by a method wherein the material in use for single-layer parison is extruded through the extrusion orifice of a cylinder and, at the same time, the material in use is pushed in the extrusion passages of multilayer head so as to plug said passages with the material in use by actuating an accumulator for accumulating the material in use for single- layer parison so as to extrude said material. CONSTITUTION:In order to change over from multilayer perison to single-layer parison, extrudes 24 and 26 of materials out of use or of material, which are used for single-layer parison, are stopped. Further, the selector values of respective hydraulic circuits are positioned so as to make the accumulating actions of accumulators 28, 30a and 30b for accumulating the materials out of use. Next, by actuating an accumulator 14 for accumulating the material in use for single-layer parison so as to extrude said material, the material in use is extruded from an extrusion orifice 2b and, at the same time, pushed in the extrusion passages 6b of a multilayer head 6 so as to plug said passages with the material in use.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for extruding parisons.

0002

BACKGROUND OF THE INVENTION A blow molding method is used to manufacture hollow containers made of resin. By blowing pressurized gas into the parison placed in the mold, a hollow container having a contour that matches the shape of the cavity can be manufactured. JP-A No. 62-99115 discloses a method in which a ring member is disposed concentrically in an annular passage for main resin, and secondary material resin is extruded from one or more annular nozzles provided in the ring member. An apparatus for extruding a multilayer parison is shown. Each annular nozzle is provided with one material inlet. As a result, for example, high-density polyethylene, which has good moldability but is permeable to gasoline, is used as the main resin for the outermost and innermost layers, and nylon resin, which does not permeate gasoline, is used as the secondary resin. A gasoline tank can be manufactured using a multilayer parison in which the intermediate layer is provided as an adhesive layer and each layer is bonded with an adhesive layer. By the way, if it is possible to efficiently switch and extrude a multilayer parison and a single layer parison using such a multilayer parison extrusion molding apparatus, the operating rate of the multilayer parison extrusion molding apparatus can be increased, which is industrially advantageous. be. Conventionally, switching from a multilayer parison to a single layer parison was performed as follows. In other words, after molding a multilayer parison using high-density polyethylene resin or nylon resin, for example, when molding a single-layer parison using only high-density polyethylene resin, the extruder for nylon resin, extruder for adhesive, etc. A resin raw material is supplied and extruded together with an extruder for high-density polyethylene resin, and the nylon resin, adhesive, etc. remaining in the extruder are extruded in a mixed state with the high-density polyethylene resin. After repeating this extrusion operation until only high-density polyethylene resin is extruded, stop the extruder for nylon resin, extruder for adhesive, etc., and drive only the extruder for high-density polyethylene resin to extrude high-density polyethylene resin. The resin was extruded as a single layer parison. By doing so, it is possible to carry out blow molding using only high-density polyethylene resin without mixing nylon resin or adhesive.

0003

[Problems to be Solved by the Invention] However, the conventional extrusion method for switching from a multi-layer parison to a single-layer parison as described above not only requires time and effort to switch from a multi-layer parison to a single-layer parison; There is a problem in that there is a lot of wasted material due to switching. Such waste of labor, time, and materials similarly occurs when switching from a single-layer parison to a multi-layer parison. The present invention aims to solve these problems.

0004

[Means for Solving the Problems] The present invention provides a method for pushing a resin material used when extruding a single-layer parison through the outlet side of an extrusion channel of an annular nozzle for resin material that is not used when extruding a single-layer parison, and plugging the resin material. The above problem is solved by making the state. That is, the parison switching extrusion method of the present invention includes a plurality of extruders (22, 22,
24, 26), a cylinder (2) having an extrusion port (2b) through which the material is extruded, a plurality of annular nozzles (6a, 6b and 6c) arranged concentrically within the cylinder (2), and Extrusion channel (6d) at the outlet of the annular nozzle
a multilayer head (6) formed with the extruder (22, 24
, 26), respectively, and accumulators (14, 28, 30) that accumulate the extruded material from the
14, 28, 30), and a multilayer parison extrusion molding device (10).
This method targets a method of switching from extrusion molding of a multilayer parison, in which different materials are overlapped and extruded, to extrusion molding of a single layer parison, and the extruders (24, 26) for materials not used in the single layer parison are stopped. , the respective hydraulic circuit (12
) is placed in a predetermined switching position, and then the accumulator (14) for accumulating material to be used for the single-layer parison is pushed out.
The material to be used is extruded from the extrusion port (2b) of 2) and pushed into the extrusion channel (6d) of the multilayer head (6) to form a plug, and non-containing material is extruded from the extrusion port (2b). The extrusion operation of the accumulator (14) is repeated while the used material is mixed in, and after the unused material is no longer mixed in, the single-layer parison is extruded. Note that the symbols in parentheses indicate corresponding members in the embodiment.

[0005]

[Operation] In order to switch the multilayer parison extrusion molding equipment from multilayer parison extrusion to single layer parison extrusion, each extruder for resin materials not used for the single layer parison (unused materials) is stopped, and the single layer parison is Only the extruder for the resin material (material used) is driven. The accumulator for the material to be used is driven to push out the material to be used. This extrusion pressure forces the used material into the extrusion channel of the unused material. As a result, the extrusion channel for the unused material is plugged with the used material. Further, due to the extrusion operation, unused material remaining near the extrusion port is discharged together with the used material. After the unused material is discharged, the used resin material is extruded. By doing so, a single layer parison can be formed. In addition, when molding a multilayer parison again after completing the molding operation with a single layer parison, if the respective extruders and accumulators are driven to extrude each material, the plugs of the extrusion channels will come off and the multilayer parison will be molded. A parison can now be formed. The first few shots will be discarded because the thickness ratio of the multilayer parison will be disturbed due to a plug in the multilayer parison extrusion molding equipment, etc., and it will be better to mold the one with the specified wall thickness ratio. good.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a multilayer parison extrusion molding apparatus 10 to which the method of the present invention is applied. The cylindrical cylinder 2 is provided with a cylindrical cylinder hole 2a in the axial direction, into which a ring-shaped piston 4 is movably fitted. The piston 4 is pushed upward in the figure by a main material resin extruded from a main material extruder 22, which will be described later, and accumulates the main material resin in the cylinder hole 2a. That is, the cylinder 2 and the piston 4 form an accumulator 14. There is an extrusion port 2 on the exit side of the cylinder 2.
b is provided. Piston 4 of accumulator 14
By pushing downward in the figure, it is possible to extrude the parison 20 from the extrusion port 2b. A substantially ring-shaped multilayer head 6 is disposed within the cylinder 2 at a portion between the piston 4 and the extrusion port 2b, away from both the inner and outer wall surfaces of the cylinder hole 2a. The multilayer head 6 is supported by a head ring 8, which will be described later. As a result, two annular outflow channels 2e and 2f are formed by the cylindrical wall surface of the cylinder hole 2a and the outer peripheral surface of the ring-shaped multilayer head 6. Extrusion port 2b of multilayer head 6
On the side facing side, three concentric annular nozzles 6a, 6
b and 6c are provided. Each annular nozzle 6a, 6b
and 6c are combined into one annular extrusion channel 6d at the outlet side end. That is, a plurality of materials are superimposed within the multilayer head 6, and then the materials are stacked together from the extrusion channel 6d to the extrusion port 2b.
It is possible to push it out to the side. A port 2c communicating with the cylinder hole 2a is provided on the circumference of the cylinder 2, and this port 2c is connected to the main material extruder 22 via a conduit 22a. Port 2 on the circumference of cylinder 2
A hole 2d that penetrates the cylinder hole 2a is provided at a position closer to the extrusion port 2b from c, and a flow path 8a is provided in this hole 2d.
, 8b and 8c are fitted and fixed together. The annular nozzle 6b located in the middle in the figure communicates with the auxiliary material extruder 24 via the flow path 8b and the pipe 24a. An accumulator 28 is provided in the conduit 24a. In addition, the annular nozzles 6a and 6c on both sides in the figure are
It communicates with the adhesive extruder 26 via the channels 8a and 26a and the pipes 8c and 26b. Conduits 26a and 26b
are provided with accumulators 30a and 30b. A rod of a hydraulic cylinder 32 is connected to the piston rod of the accumulator 14, as shown in FIG. Two ports of the hydraulic cylinder 32 are connected to A of the switching valve 34.
, B port, respectively. P of switching valve 34
The port is connected to a hydraulic power source 38 via a proportional electromagnetic relief pressure reducing valve 36 . The T port of the switching valve 34 is connected to the tank 40. Proportional solenoid relief pressure reducing valve 3
By adjusting 6, the flow rate of oil supplied to the hydraulic cylinder 32 can be adjusted. This makes it possible to change the extrusion speed at which the main resin in the accumulator 14 is extruded. A hydraulic circuit 12 is formed by a hydraulic cylinder 32, a switching valve 34, a proportional electromagnetic relief pressure reducing valve 36, a hydraulic source 38, a tank 40, and the like. Accumulator 28, accumulators 30a and 3
The piston rods 0b are also each connected to a rod of a hydraulic cylinder 32, and each hydraulic cylinder 32 is connected to a hydraulic circuit similar to the hydraulic circuit 12 of the accumulator 14.

Next, the operation of this embodiment will be explained. The multilayer parison extrusion molding apparatus 10 is adapted to extrude a multilayer parison. That is, the main material resin accumulated in the cylinder hole 2a from the main material extruder 22 through the pipe line 22a and the flow path 2c is pushed out to the outflow channels 2e and 2f by the extrusion operation of the accumulator 14, and the outermost layer and The innermost layer is formed, and the secondary material resin extruded from the accumulator 28 of the secondary material extruder 24 through the flow path 8b to the annular nozzle 6b forms an intermediate layer, and the adhesive extruder 2
6 accumulators 30a and 30b to the flow path 26a.
Annular nozzles 6a and 6c pass through 8a and 26b and 8c.
The extruded adhesive forms an adhesive layer between the layers. The intermediate layer and the adhesive layer are extruded from the extrusion channel 6d in a superimposed state, superimposed on the outermost layer and the innermost layer of the main resin, and extruded from the extrusion port 2b as a multilayer parison. A multilayer hollow container can be formed from this multilayer parison. During extrusion of a multilayer parison, the respective switching valve 34 is in the symbolic position shown in FIG. It can be switched alternately as shown in the middle right symbol position. Suppose that it becomes necessary to switch from extruding a multilayer parison to, for example, molding a single-layer hollow container using only the main resin. First, all extruders 22, 24 and 26 are stopped. The respective switching valves 34 for the accumulators 28, 30a and 30b are then placed in the symbol positions shown in FIG. That is, the upper port in the figure of the hydraulic cylinder 32 is communicated with the tank 40 via the switching valve 34. Next, by driving the main material extruder 22 to push out the main material resin into the cylinder hole 2a, the accumulator 1
The main resin is accumulated by pushing the piston 4 upward in the figure. By switching the switching valve 34 that operates the piston 4 to the symbol position on the right in FIG. 2 and moving the piston of the hydraulic cylinder 32 downward in the diagram, the pipe line 22a
, the main resin is extruded from the outflow channels 2e and 2f toward the extrusion port 2b through the channel 2c and the like. Due to this extrusion pressure, the main material resin is extruded from the extrusion port 2b and enters the extrusion channel 6d of the multilayer head 6 to form the annular nozzle 6.
Push the auxiliary resin and adhesive in a, 6b, and 6c upward in FIG. This causes the pistons of the accumulators 28, 30a and 30b to move in the direction of increasing volume, and the pistons of the respective hydraulic cylinders 32 to move as well (the respective hydraulic cylinders 32 for the accumulators 28, 30a and 30b are shown in FIG. , since the upper oil chamber communicates with the tank 40, the movement of the pistons of the respective hydraulic cylinders 32 is not hindered). Therefore, a part of the main resin enters the extrusion channel 6d of the multilayer head 6 and becomes plugged. Most of the main resin is extruded from the extrusion port 2b. By continuing the extrusion operation by the accumulator 14, the extrusion channel 6d and the extrusion port 2
The auxiliary resin and adhesive remaining between the spaces b are extruded from the extrusion port 2b, and finally only the main resin is extruded from the extrusion port 2b. That is, the switching from the multilayer parison to the single layer parison is completed. In this state, a single layer parison is extruded using the main resin. This makes it possible to mold a hollow container using only resin as the main material. After completing the molding of a hollow container using a single-layer parison made of only resin as the main material,
When it becomes necessary to mold a hollow container using a multilayer parison again, the auxiliary material extruder 24 and the adhesive extruder 26 are driven. The switching valves 34 for the accumulators 28, 30a and 30b are switched to the right symbol position in FIG. As a result, the accumulators 28, 30a, and 30b move in the extrusion direction and pass through the flow paths 8a, 8b, and 8c to the annular nozzle 6.
Apply pressure to a, 6b, and 6c. As a result, the plug of the main material resin stuck in the extrusion channel 6d of the multilayer head 6 is removed, and the sub-material resin and adhesive are extruded in a layered form from the extrusion channel 6d. The secondary material resin and adhesive are extruded from the extrusion port 2b in a state where they form a multilayer parison together with the main resin layer from the outflow channels 2e and 2f. The first few shots are discarded because the wall thickness ratio of the multilayer parison is disturbed due to the presence of the stopper, etc., and the shot having a predetermined wall thickness ratio is used for molding a multilayer container. (Test example) High-density polyethylene resin as the main resin,
Nylon resin was used as the auxiliary resin, and these were extruded together with an adhesive to form a multilayer parison. The temperature of the multilayer head 6 of the multilayer parison extrusion molding apparatus 10 was 240°C. From this state, the sub-material extruder 24 and the adhesive extruder 26 are stopped, and the accumulator 28,
The switching valves 34 of 30a and 30b were located at the symbol positions shown in FIG. 2, respectively. In this state, the accumulator 14 for the main material extruder 22 was operated to extrude the high-density polyethylene resin. By repeating the extrusion operation of the accumulator 14 several times, the high-density polyethylene resin was forced into the extrusion channel 6d of the multilayer head 6 to form a plug. At the same time, the nylon resin and adhesive remaining around the extrusion port 2b were discharged. The operation of extruding the high-density polyethylene resin as a single-layer parison from the main material extruder 22 was repeated 25 times, but no contamination of the nylon resin or adhesive was observed. Note that each time a single layer parison is extruded, the accumulators 28, 30a and 3
It was observed that the piston of 0b moved by a minute amount in the direction of increasing capacity. In other words, each time a single-layer parison was extruded, the plug was gradually made longer. Also, when switching from extruding a multilayer parison to extruding a single layer parison, the accumulators 28, 30a and 3
The switching position of the switching valve 34 for 0b is located at the central symbol position in FIG.
The extrusion operation of the single-layer parison was repeated 10 times with the pistons 30a and 30b locked so that they did not move in the volume increasing direction, but in this case, nylon resin and adhesive were found to be mixed in all 10 times. . From this, in order to extrude a single-layer parison using a multi-layer parison extrusion molding device, the resin for the single-layer parison is pushed into the extrusion channel 6d of the material not used in the single-layer parison, so that it can form a plug. I understand that it is necessary.

[0008]

As explained above, according to the parison switching extrusion method of the present invention, switching between a multilayer parison and a single layer parison can be performed in a short time. Furthermore, the amount of resin wasted due to switching can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a blow molding machine having a multilayer parison extrusion molding device.

FIG. 2 is a piston operation circuit diagram of an accumulator.

[Explanation of symbols]

2 Cylinder 2b Extrusion port 2e/2f Outflow channel 6. Multilayer head 6a/6b/6c Annular nozzle 6d Extrusion channel 10 Multilayer parison extrusion molding equipment 12 Hydraulic circuit 14 Accumulator 22 Extruder 24 Extruder 26 Extruder 28 Accumulator 30a/30b Accumulator 34 Switching valve

Claims (1)

[Claims] [Claim 1] A plurality of extruders that extrude different materials (
22, 24, 26) and an extrusion port (2) through which the material is extruded.
b) with a plurality of annular nozzles (6a, 6b and 6c) arranged concentrically within the cylinder (2);
) is formed and an extrusion channel (
6d) and an extruder (22).
, 24, 26);
A multilayer parison extrusion molding apparatus (10) having a hydraulic circuit (12) that drives an accumulator (14, 28, 30a, 30b) is used to extrude a multilayer parison by overlapping and extruding different materials. Switching to extrusion of layered parisons In the extrusion method of parisons, an extruder (
24, 26) respectively, and the switching valves (34) of the respective hydraulic circuits (12) are set to predetermined switching positions so that the accumulators (28, 30a, 30b) that accumulate unused materials can perform the accumulation operation. an accumulator (14
), the material to be used is extruded from the extrusion port (2b) of the cylinder (2), and the material to be used is pushed into the extrusion channel (6d) of the multilayer head (6) to form a plug, and While the unused material is mixed in the used material extruded from the accumulator (14
) A parison switching extrusion method in which a single-layer parison is extruded after repeating the extrusion operation until no unused materials are mixed in.